Lithium triethylborohydride ‘Superhydride

Other reagents used for the preparation of lactones from acid anhydrides are lithium borohydride [1019], lithium triethylborohydride (Superhydride ) [1019] and lithium tris sec-butyl)borohydride (L-Selectride ) [1019]. Of the three complex borohydrides the last one is most stereoselective in the reduction of 3-methylphthalic anhydride, 3-methoxyphthalic anhydride, and 1-methoxynaphthalene-2,3-dicarboxylic anhydride. It reduces the less sterically hindered carbonyl group with 85-90% stereoselectivity and is 83-91% yield [1019]. 

Li[Et3BH] (Superhydride) (lithium triethylborohydride) Tetrahydrofuran -78 to RT ester —> alcohol ketone —> alcohol aldehyde —> alcohol alkyl halide —> alkane epoxide —> alcohol... 

Another modified metal hydride, lithium triethylborohydride, the so-called superhydride , has been introduced as a powerful reducing agent especially suitable for trisubstituted, tetrasubstituted and bicy-clic epoxides (Table 3). With trisubstituted epoxides the regiochemistry is completely controlled to give only tertiary alcohols. No skeletal rearrangement is observed for benzonorbomadiene oxide. 

With respect to the palladium-catalyzed reductive desulfonylations of allylic sulfones, [PdCl2(dppp)] is the preferred catalyst in combination with superhydride (LiHBEts) in THF solutions, usually working under low temperature (0-4°) to room temperature conditions. Lithium triethylborohydride is supplied as a 1 M solution in tetrahydrofuran and is corrosive and flammable. Handle and store under an inert atmosphere in a cool dry place. Use the solution in a fume hood and avoid contact with skin. 

---